1. Field of the Invention
The invention relates to air filters and, more particularly, to heavy duty air filters including a gasket mounted thereon to prevent the flow of unfiltered air about the filter.
2. Summary of Related Art
Air filters are well known devices wherein air is drawn or forced into a housing and caused to pass through a filter unit having a full flow filter media to remove the dirt and dust particles carried in the air. Substantially clean air is thereby passed to the point of usage, such as an internal combustion engine. Large, heavy duty air filters are utilized on heavy equipment, such as trucks and earth movers. Such air filters have heretofore generally included an annular foamed rubber gasket bonded to the substantially flat end cap of the filter unit with an adhesive. The gasket seals the inlet from the outlet of the housing, so that no air will pass through the outlet without first having passed through the filter unit. Typically, the gasket is compressed between the end cap of the filter unit and the end wall of the housing by the manual tightening of a bolt which urges the filter unit into sealing engagement against the end wall of the housing.
While the mounting of the foamed rubber gasket to the end cap by means of an adhesive is almost universally practiced, and has been for many years, this construction has a number of disadvantages, the significance of which were not heretofore appreciated. Thus, the gasket, which in air filters is generally formed of a foamed rubber material, tends to lose its stability and concentricity as the filter unit is forced against the housing end wall. Further, it is believed that users often overtighten the bolt, thereby subjecting the gasket to excessive compressive forces and potentially causing permanent deformation of the gasket. As a result, the integrity of the seal provided by the gasket is often compromised. Finally, the bonding of the gasket to the housing end cap makes it difficult if not impossible to remove and replace the gasket. Replaceability of the gasket is desirable if, for example, the filter unit is of the type which is cleaned and reused.